The term “On-Board Diagnostics” (OBD) refers to a computer-based monitoring system built into vehicles. For example, in the United States, model year 1996 and newer light-duty cars and trucks include OBD systems. The OBD system may monitor the performance of some of an engine's components. For example, an OBD system may provide vehicle owners with an early warning of malfunctions by way of a dashboard “Check Engine” light.
Vehicles equipped with an OBD system may include a standardized hardware interface port (e.g., an OBD port) through which an external device may be connected. The device may communicate with the OBD system to receive diagnostic information relating to the operation of the vehicle.
Emissions of air pollutants from motor vehicles have been shown to have a variety of negative effects on public health. Accordingly, many jurisdictions require that vehicle operators periodically have their vehicle tested to verify that the vehicle complies with emissions standards. A vehicle's OBD system may be used to implement vehicle emission inspections. For example, an OBD inspection device may be connected to a vehicle through the OBD port of the vehicle. The OBD inspection device may then receive diagnostic information, such as information relating to the operational state of emission control components within the vehicle. The diagnostic information may be used to determine whether the vehicle complies with emission standards.